Dismounting Kerbs: Advanced Approach

[Gihgehls]

The trick is to not be accelerating or decellerating by the time you get to the curb. You have to make sure that the platform is level when you fly off of it. Doing it as shown in the video leaves the opportunity to accidentally go backwards, leading to tragedy.

[Bob.Kerns]

Originally Posted by Gihgehls

The trick is to not be accelerating or decellerating by the time you get to the curb. You have to make sure that the platform is level when you fly off of it. Doing it as shown in the video leaves the opportunity to accidentally go backwards, leading to tragedy.

Accelerating shouldn't pose a problem, right? Nor, for that matter, should a deacceleration, so long as it's small compared to the speed? And if you did reverse and hit the curb, you'd be going rather slowly, and the possibility would exist to simply step off, and avert the tragedy?

That last isn't intended to deny it's a risky situation -- just a way out. I suppose an intentional simultaneous drop-and-dismount could be done, and avoid the unpleasant drop while being quick. But I think I'd still have the battery-strike issue, so I don't think I'll be trying it.

I hit an up curb once (misalignment at a curb cut), and it didn't go, and stepped off. Going slowly; I was able to step BACK, and of course it then popped right up over the curb, and I wrestled it to a standstill. I regretted getting off, though -- it startled a nearby pedestrian-rights activist and flushed him out of hiding, and I got another spurious lecture about what I was doing being supposedly illegal and how dangerous these things were.

(This was in San Francisco, of course).

No such thing, of course, it just occupied the space I was about to enter, and I continued to occupy the space I had desired to leave -- both of which were empty.

But it would have been more smoothly handled to just back up a few inches and retry, without the dismount.

In fact, that might make a good video -- up against some small obstruction, get stick shake, lean back and forward again, and roll on over.

[KSagal]

I don't understand this comment about curb strikes on the battery...

The battery does not extend beyond the tires in any direction, so if the curb is straight where you go off, as long as both tires leave at the same time, the battery cannot hit.

If you go off the curb one wheel at a time(at an angle), you can hit the battery while the seg is one wheel up and one wheel down.

If you go off a curving curb, or off a corner, you can strike the battery but not otherwise...

On a slightly different note, I have had a hitch on the back of my seg since 2003, and it does extend beyond the line of the tires, but only slightly. Because of this, I always glide down curbs, when I must, at a couple miles per hour. This will give enough distance from the curb when the seg travels vertically down the face to have it not hit my hitch...

Furthermore, gliding down too slow is dangerous in that new gliders especially will have a tendency to lean back a bit in an effort to reduce their speed as they transition from horizontal movement to vertical movement at the edge of the curb... This means that the seg is tending to back up at the moment it hits the bottom, and the jarring of the landing, with the backing up of the segway against the curb face can be hard to deal with...

For all these reasons, I suggest a modest speed of 2 or 3 mph for curb drops... More than that is not needed, but the seg is easier to deal with if moving at a modest pace in this environment, in my opinion...

Still, I endorse the videos I have seen so far, as very reasonable, and a useful tool and starting point for low hour seggers.

[Bob.Kerns]

I certainly didn't expect battery strikes, for the very reasons you state.

These are straight-off-the-curb exits, straight curbs, with reasonably sharp edges on the curbs. The only way I could see for it to happen is for the curb edges to be indenting the tires under the 260 pounds or so of load (+ Segway).

I do keep my tires fully inflated.

At some point, I'll try some static experiments. In the meantime, I try to have some forward velocity on the rare occasions I do such maneuvers.

[gbrandwood]

Originally Posted by Gihgehls

The trick is to not be accelerating or decellerating by the time you get to the curb. You have to make sure that the platform is level when you fly off of it. Doing it as shown in the video leaves the opportunity to accidentally go backwards, leading to tragedy.

There is always the opportunity for something to go wrong - and the potential for leaning backwards is pointed out in the guide notes which accompany the videos. This is why the approach is dubbed the advanced approach, as opposed to the approach a beginner should use. And certainly, the advanced approach may be less necessary on smaller kerbs and I wouldn't expect a newbie to try the advanced approach on a tall kerb or indeed sail off the kerb at speed.

Originally Posted by Bob.Kerns

Accelerating shouldn't pose a problem, right?

I think it would pose a problem. Again, I've had a bash at describing this in my guide but essentially, if your wheels leave the ground (traction) and you are level, i.e. not accelerating or braking, the wheels will turn at the same speed they turned whilst on the ground. Accelerating or braking during "air-time" instructs the PT to spin up the wheels faster or slower. The PT says, hold on, there's no traction here, spins up the wheels to top speed then shuts down. You don't want that to happen - but is only really likely if you catch a lot of air or make significant changes to the platform angle.

Originally Posted by Bob.Kerns

But it would have been more smoothly handled to just back up a few inches and retry, without the dismount.

In fact, that might make a good video -- up against some small obstruction, get stick shake, lean back and forward again, and roll on over.

I mention this in my guide but no video. I think you're right, it might make a good video and will add it to the list. I need to start repeating the vids on an i2, x2 etc.

[gbrandwood]

Originally Posted by KSagal

Furthermore, gliding down too slow is dangerous in that new gliders especially will have a tendency to lean back a bit in an effort to reduce their speed as they transition from horizontal movement to vertical movement at the edge of the curb... This means that the seg is tending to back up at the moment it hits the bottom, and the jarring of the landing, with the backing up of the segway against the curb face can be hard to deal with...

For all these reasons, I suggest a modest speed of 2 or 3 mph for curb drops... More than that is not needed, but the seg is easier to deal with if moving at a modest pace in this environment, in my opinion...

Still, I endorse the videos I have seen so far, as very reasonable, and a useful tool and starting point for low hour seggers.

Agreed and thanks.

[Bob.Kerns]

Originally Posted by gbrandwood

I think it would pose a problem. Again, I've had a bash at describing this in my guide but essentially, if your wheels leave the ground (traction) and you are level, i.e. not accelerating or braking, the wheels will turn at the same speed they turned whilst on the ground. Accelerating or braking during "air-time" instructs the PT to spin up the wheels faster or slower. The PT says, hold on, there's no traction here, spins up the wheels to top speed then shuts down. You don't want that to happen - but is only really likely if you catch a lot of air or make significant changes to the platform angle.

You're only dropping a few cm. A 10 cm curb is only 71 ms. I'm pretty sure it doesn't shut down in this short a time under any circumstance; it would be unsafe. And I doubt it spins the wheels arbitrarily fast, either; it won't add traction. It has tight control over the motor speed.

If you're leaning forward, you'll NEED an extra bit of push when you hit to restore balance.

I'm not arguing you should recommend accelerating, though! I don't even recommend routinely leaping off curbs. It's hard on device and rider both. I'd consider it more of an emergency maneuver. I know there are those that consider it great fun. I'd rather treat my machine gently, and myself as well.

[Gihgehls]

Originally Posted by KSagal

I don't understand this comment about curb strikes on the battery...

You're only considering curbs without curves if you don't understand. There are curbs you could go down in which the wheels will be clear of the curb before the center of the platform is.

Originally Posted by Bob.Kerns

Accelerating shouldn't pose a problem, right? Nor, for that matter, should a deacceleration, so long as it's small compared to the speed?

Like brandwood says, changing the platform angle while there is zero traction leads to an unhappy segway and a riskier landing. If you've never seen how fast the wheels will spin up in this instance you would be amazed if you did. Think of the full force of the 2.5 HP motors spinning up to max speed. I'd estimate they get up past 20 mph before the seg shuts down, and they spin up in probably less than a 3rd of a second. It's a scary amount of power.

[gbrandwood]

Bob, you can test this. Put your PT on a stool so the wheels are both free to move. Press the mat to engage balance
mode. The wheels won't do much yet. Now, tilt the Segway forward slightly. Watch the wheels rev up and frighten the life out of you. This is what I was describing. Now, if you're not in the air too long, this might not occur but the faster you leave the kerb, the more chance it will get. Plus, they don't need too rev all the way up to cause you a problem.

[KSagal]

Originally Posted by KSagal

I don't understand this comment about curb strikes on the battery...

The battery does not extend beyond the tires in any direction, so if the curb is straight where you go off, as long as both tires leave at the same time, the battery cannot hit.

If you go off the curb one wheel at a time(at an angle), you can hit the battery while the seg is one wheel up and one wheel down.

If you go off a curving curb, or off a corner, you can strike the battery but not otherwise...

On a slightly different note, I have had a hitch on the back of my seg since 2003, and it does extend beyond the line of the tires, but only slightly. Because of this, I always glide down curbs, when I must, at a couple miles per hour. This will give enough distance from the curb when the seg travels vertically down the face to have it not hit my hitch...

Furthermore, gliding down too slow is dangerous in that new gliders especially will have a tendency to lean back a bit in an effort to reduce their speed as they transition from horizontal movement to vertical movement at the edge of the curb... This means that the seg is tending to back up at the moment it hits the bottom, and the jarring of the landing, with the backing up of the segway against the curb face can be hard to deal with...

For all these reasons, I suggest a modest speed of 2 or 3 mph for curb drops... More than that is not needed, but the seg is easier to deal with if moving at a modest pace in this environment, in my opinion...

Still, I endorse the videos I have seen so far, as very reasonable, and a useful tool and starting point for low hour seggers.

[quote=Gihgehls;181960]You're only considering curbs without curves if you don't understand. There are curbs you could go down in which the wheels will be clear of the curb before the center of the platform is.
...quote]


I don't understand your statement. I stated that I knew that a curve in the curb at the point where you go over it can cause a battery strike. Your comment did not take into affect all that I said...

The comments that I had said I did not understand were those that stated that the curb was straight, yet there was still a battery strike. That is the part I did not understand...